Types Of Rocks

By: Kate Golwas

Igneous rocks are formed from cooled magma, or lava. The lava cools in about ten to fifteen minutes, so these rocks form very quickly. Heat is needed to form these rocks. Igneous rocks can remelt to change into other forms of igneous rocks. Examples of igneous rocks are granite, obsidian, and gabbro.

The next type of rock is called sedimentary. These rocks are formed when sediments are pressed and cemented together in layers. No heat is needed to form these rocks. Cemented, compact, and layers are words to describe how these rocks form. Examples of these rocks are limestone, sandstone, and breccia. These rocks may take millions of years to form.

The last types of rocks are called metamorphic rocks. These rocks are formed when another type of rock is squeezed and heated inside earth's crust. Beside's heat these rocks also need pressure to form. These rocks are formed from igneous or sedimentary rocks. They get out from under the surface of the earth during the process of erosion. Examples of these rocks are marble, slate, and gneiss.

These are the three main types of rocks. This video is also about these rocks. This is a short fifty second video, and I hope you learn a lot.